1. Field of Invention
The present invention relates to an electronic apparatus and more particularly, to a portable electronic apparatus.
2. Description of Related Art
In the modern information era, people are becoming more and more dependent on portable electronic apparatus such as cellular phones, electronic dictionaries, personal digital assistants (PDAs), and handheld game consoles that are commonly seen in people's daily lives. Take cellular phones for example, various manufacturers devote research effort to minimizing weight and dimensions of cellular phones so as to provide users with portability. However, minimizing dimensions of cellular phones inevitably involves utilizing limited space to maximize sound quality.
A common cellular phone has a case and a speaker. The case has a sound hole. The speaker is disposed in the case and corresponds to the position of the sound hole. Between a front end of the speaker and the case, there forms a front sound chamber. A layer of foam is disposed between the front end of the speaker and the case to maintain a spatial distance therebetween. In addition, between a back end of the speaker and the case, there forms a back sound chamber. The speaker includes a magnet, a voice coil, and a vibration board. The operation theory of the speaker is that the magnet forms a magnetic loop and electric current passes through the voice coil disposed in the speaker, which generates a driving force in an up-down direction and causes the vibration board to vibrate. At this time, air vibrated by the vibration board generates sound. Sound waves generated by the vibration of the vibration board are transmitted between the front sound chamber and the back sound chamber without phase interference and thus sound quality is promoted.
However, the back sound chamber in the abovementioned design can not have an entirely closed space due to influence of chinks in the assembly of the case and an earphone plug hole on the case. Therefore, sound leakage may occur and sound quality is affected. Another design uses an injection molding technique to inject a case fully covering a speaker and forming an entirely closed back sound chamber between the case and the speaker. Although an entirely closed back sound chamber may promote sound quality, a case has to be injected to fully cover a speaker and manufacturing costs are thereby increased. Furthermore, a speaker and plastic are injection molded at the same time so the speaker can not be freely detached, which also increases maintenance burden.